1. Field of the Invention
The present invention relates to an anaesthesia set, and in particular to an anaesthesia set comprising a straight epidural cannula with a ground opening, a spinal cannula which is longer and thinner than the epidural cannula and which can be inserted into the epidural cannula such that its front end projects from the epidural cannula, and a catheter adapted to be advanced through the epidural cannula.
2. Description of Related Art
When operating on the lower extremities and the organs in the pelvis, regional anaesthesia is substantially performed as spinal anaesthesia or epidural anaesthesia The advantages of spinal anaesthesia include: a quick effect, hardly any failures and a mostly complete analgesia. Among the drawbacks of spinal anaesthesia are that it is effective only approximately up to the hip, that the duration of the effect is limited with single shots, and that the introduction of a catheter into the spinal space can cause infections.
When performing spinal anaesthesia, a set of the above-mentioned type may be used (German Utility Model 88 11 408). In such a case, the cannula is a so-called Crawford cannula, the straight front tip of which is shortly bevelled and ground. The edges of the grinding are rounded in order to reduce the risk of a perforation of the dura. The thinner spinal cannula is advanced through the coaxial terminal opening of the epidural cannula to perforate the dura, and the catheter is advanced over a guide wire through the epidural cannula into the spinal space. An analgetic may be subsequently injected through the catheter (by means of a syringe, for example), at the extracorporeal end of which a connector is fixed.
In epidural anaesthesia, a catheter is introduced into the spinal space through an epidural cannula. This is less critical than it is in spinal anaesthesia. An optional duration of analgesia by subsequent injections and postoperative analgesia may be obtained. With the use of suitable analgetics, the analgesia may be maintained when the motorial function is restored. Although the effect occurs later than with spinal anaesthesia, epidural anaesthesia has an advantage over spinal anaesthesia in that it is effective up to the breast.
Thus, a combination of spinal and epidural anaesthesia, thereby combining the specific advantages of both techniques, could result in an extension of the region of the anaesthesia. However, the known sets for epidural anaesthesia do not allow a combination without risks. This is due to the fact that the dura is perforated by the advancement of the spinal cannula through the epidural cannula to inject an analgetic, and the epidural catheter (which is also advanced through the epidural cannula) contacts the dura at exactly the spot where it has previously been perforated. As a result, the epidural catheter will introduce the analgetic meant for the epidural space into the spinal space. This not only increases the anaesthetic risks to the patient, but also fails to spread the analgetic effect to that part of the body intended to be anaesthetized by the epidural anaesthesia.
It is an object of the present invention to provide an anaesthesia set of the type mentioned above such that it allows a simple and riskless use in combined spinal and epidural anaesthesia.